Charged-particle scanning microscopy has become a very important tool for examination of specimens having microscopic-scale and/or nanoscale features. Scanning electron microscopy is a versatile form of charged-particle scanning microscopy that is extensively used in the biological sciences and in physical sciences and technology, especially in microelectronics development and manufacturing. The utility and versatility of a scanning electron microscope (SEM) arises in part from the various modes of image formation that an SEM can employ, such as secondary electron emission, Auger electron emission, backscattered electron contrast, cathodoluminescence, characteristic X-ray emission, and electron-bean induced current (EPIC). Several of these modes are susceptible to interference by magnetic fields that may be present in the vicinity of a specimen being examined. In microelectronics development and manufacturing, the SEM is often used for defect and yield analysis of semiconductor integrated circuits.
Specimens to be examined in an SEM are often mounted on conductive specimen stubs, e.g., with conductive paste. Such electrical contact to a specimen mounted on such a stub may be required to prevent charging of the specimen during scanning with the electron beam or other charged-particle beam. Some modes of using SEM's require at least one electrical contact in addition to back side contact to a stub. The electron-beam induced current (EPIC) mode is such a mode.
Various special-purpose stages have been developed for use in SEM's and other charged-particle-beam instruments, such as electron-beam and ion-beam lithography systems. For example, special-purpose stages have been made for heating specimens, for cooling specimens to low temperatures, for tensile-strength testing in an SEM, for wet specimens, for scanning transmission electron microscopy (STEM), for combination SEM and scanning probe microscopy, etc.
Using a charged-particle-beam scanning instrument such as an SEM for defect and yield analysis of semiconductor integrated circuits in microelectronics development and manufacturing, for example, often requires examination of multiple specimens in electron-beam induced current (EPIC) mode. As each new specimen has been introduced into the instrument, it has been necessary to re-position electrical contacts on the new specimen, a time-consuming process that is sometimes difficult to perform reproducibly so that various specimens will be examined with equivalent corresponding electrical-contact arrangements. Thus, there is a need for a specimen stage that allows fast, convenient, and repeatable specimen exchanges with repeatable electrical contacts in a charged-particle-beam scanning instrument.